What are the adaptive advantages of a lack of hair in animals?
The primary function of hair is for thermoregulation. Elephants and rhinoceroses are large animals which have very low surface area to volume ratios, and live in warm climates, and have no need of hair to keep warm. In contrast the woolly mammoth, had lots of long hair and was adapted for cold climates. Other mammals with little hair might include hippos, whales, the naked mole rat, and manatees/dugongs. The whales have low surface to volume ratios, insulating blubber, and presumably have eliminated most hair to cut down on drag in the water. Technically they do still have hair. The filters they use to collect food are keratin based and grow from highly modified hair follicle-like structures. Manatees live in warm coastal tropical waters and have no need for hair. The mole rat lives in a hot climate and stays underground pretty much all the time. Some domestic animals such as pigs or pets such as the sphinx breed of cats have very little hair. It is either short or sparse. These strain
